A teammate who notices fatigue can prevent confidence from becoming a poor decision.

Tiredness does not feel like tiredness from inside. It feels like clarity, like impatience with caution, like being ready to just decide and move on. That is exactly when the expensive mistakes get made, and it is almost impossible to catch in yourself because the faculty you would use to catch it is the one that is depleted. Someone standing next to you can see it in a second.

Give one person permission to say you look tired and mean it as information, not insult. Then, when they do, postpone the decision rather than defending it.